This invention relates to cable-handling equipment and, more particularly, to a level winder for a winch.
A level winder controls the path of a cable as it is wound on the drum of a winch so the cable is wrapped in contiguous helical turns extending from edge to edge of the drum without crossing over one another. As used herein, the term cable encompasses steel cable, rope, wire, and other types of lines for tensional transmission of force. Such a configuration of continuous edge-to-edge helical turns provides the most efficient utilization of storage space on the drum, permits the smoothest and most reliable payout of cable from the drum, and protects the cable from damage. Steel cables are particularly vulnerable to damage because of their limited flexibility. If one turn of a steel cable jumps off the prescribed contiguous helical path and crosses over another turn, the steel cable is subjected to a much sharper bending arc at the point of crossover than the bending arc presented by the drum, which, depending on the tension on the cable frequently permanently deforms, weakens, and destroys the cable. For these reasons, it is important that a level winder operate efficiently and reliably.
The diameter of a cable changes as a function of the tension exerted thereon, depending upon the modulus of elasticity of the cable material. Presently available level winders have a cable guide that is mechanically coupled to the drum by reversible gearing or screw threads so as to be driven responsive to the rotation of the winch. Such arrangements are generally not able to adjust the pitch of the helical turns as the cable diameter changes. Thus, in order to prevent crossing of the cable or gaps between helical turns, the cable tension must be maintained within prescribed limits.